Cosmology with active galactic nuclei

我在观测宇宙学的研究集中在活动星系核（AGN），通常被称为类星体，巨大的光度明亮的恒星物体，大型星系的发电站中心。了解这些天体是至关重要的，因为它们必须参与星系的形成和演化-它们的性质与宿主星系的性质密切相关。无论它们的物理学有多么神秘，它们都是能够在整个可观测宇宙中追踪质量的发光灯塔。我的建议涉及到活动星系核研究的两个方面：（1）射电活动星系核的“统一模型”认为射电类星体和射电星系是相同的--不同的外观仅仅是涉及中央环面和相对论性光束的投影效应。如果我们的视线与投影轴重合，我们看到的是类星体，否则就是双叶射电星系。1997年至1999年的研究向我们展示了如何利用类星体和射电星系的大量统计数据来获得活动星系核光束系统的物理学。我们现在有大量的新数据，使我们能够正确地进行分析。因此，通过对体统计的分析，我们可以建立宇宙中最明亮物体的核心物理学-我们可以找到类星体的工作原理。(2)我的第二个项目是关于暗能量。我们目前的“和谐宇宙学”认为宇宙中5%的物质是发光的，25%是黑暗的，无法直接观察到，75%被推断为未知性质的暗能量。暗能量存在的直接保证可以通过“集成萨克斯-沃尔夫”（ISW）效应来实现：只有当宇宙目前由暗能量主导时，无线电测量中源表面密度的数量波动与宇宙微波背景的波动之间的相关性才能产生。其他人的早期测试是积极的，与推断一致。我希望在一次大型射电巡天中使用一个源的质量识别程序，计算出巡天中每个红移壳层对相关的贡献。这将定义暗能量属性作为宇宙时代的函数，限制其性质。这是一个新的工具，可以用来探索宇宙学中最具挑战性的问题。

My research in Observational Cosmology concentrates on Active Galactic Nuclei (AGNs), commonly known as quasars, bright stellar objects of enormous luminosity, the powerhouse centres of large galaxies. It is vital to understand these objects as they must be involved in galaxy formation and evolution - their properties are tightly correlated with those of the host galaxies. Whatever their mysterious physics, they are luminous beacons able to trace mass throughout the observable universe. My proposal concerns two aspects of my AGN research:(1) The 'unified model' of radio AGN has it that radio quasars and radio galaxies are the same  - the different appearance is simply a matter of projection effects involving a central torus and relativistic beaming. We see a quasar if our line-of-sight coincides with the projection axis, a double-lobed radio galaxy otherwise. Research 1997 to 1999 showed us how we could use bulk statistics of quasars and radio galaxies to obtain the  physics of AGN beaming systems. We now have a flood of new data to allow us to do the analysis properly. Thus through analysis of bulk statistics, we can establish the central physics of the most luminous objects in the Universe - we can find how quasars work.(2) My second project concerns Dark Energy. Our current 'concordance cosmology' has 5% of the matter in the Universe as luminous, 25% as dark and unobservable directly, and 75% inferred as Dark Energy of unknown nature. Direct assurance of Dark Energy existence can come through the 'Integrated Sachs-Wolfe' (ISW) effect: a correlation between number fluctuations in the surface density of sources in a radio survey and fluctuations in the cosmic microwave background could only result if the Universe were currently dominated by Dark Energy. Early tests by others have been positive, in agreement with inference. I wish to use a programme of mass identifications of the sources in a large radio survey to work out the contribution to the correlation in each redshift shell of the survey. This will define Dark Energy  properties as a function of cosmic epoch, constraining its nature. Here is a new tool with which to explore the most challenging issue in cosmology.